Method of implanting a lead for brain stimulation

ABSTRACT

Leads and introduction tools are proposed for deep brain stimulation and other applications. Some embodiments of the present invention provide lead designs with which may be placed with a stylet, while others do not require a stylet. Some lead embodiments use standard wire conductors, while others use cable conductors. Several embodiments incorporate microelectrodes and/or microelectrode assemblies. Certain embodiments of the present invention provide introduction tools, such as cannula and/or cannula systems, which ensure proper placement of, e.g., leads.

The present application is a Divisional of application Ser. No.10/035,745, filed Dec. 28, 2001, to be issued as U.S. Pat. No. 7,033,326on Apr. 25, 2006 which application claims the benefit of U.S.Provisional Patent Application Ser. No. 60/258,767, filed Dec. 29, 2000,which applications and patent are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to medical leads and systems,and more particularly relates to lead systems and methods of introducingleads for brain or other stimulation.

BACKGROUND OF THE INVENTION

Deep brain stimulation (DBS) in the thalamus for the treatment of tremorwas approved by the FDA in 1997. Subsequently, it has been found thatstimulation in various areas of the brain may be useful for treating avariety of conditions, including providing relief from symptoms ofParkinson's disease and other diseases.

In July 2001, the National Institute of Neurological Disorders andStroke and the National Institute of Mental Health reported that overtwo thousand patients have been implanted with DBS systems, and that thenumber was growing rapidly. Using current guidelines, estimations arethat as many as 15,000 individuals per year may be candidates for thisprocedure. This number could increase as the population ages and/or ifthe indications are expanded.

SUMMARY OF THE INVENTION

The invention disclosed and claimed herein provides advances in leadsand introduction tools which are useful in deep brain stimulation andother applications. Some embodiments of the present invention providelead designs with a tip electrode, some with an insulating material atthe distal tip, and these tips may be rounded. Some of these leads maybe placed with a stylet, while others do not require a stylet. Certainlead embodiments have a through-hole that allows the lead and amicroelectrode to be advanced and retracted in relation to one another.Some lead embodiments use standard single-wire conductors, while othersuse cable (i.e., multi-strand or multi-wire) conductors. In someembodiments, the cable conductors make the stylet and stylet lumenunnecessary. Other embodiments provide various lead shapes. Additionalembodiments of the present invention provide introduction tools, such ascannula and/or cannula systems.

The leads and introduction tools of the present invention may be usedwherever an electrical lead is required, or wherever a similarly shapeditem, such as a catheter or a chronic DBS lead, is introduced into abody.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the present invention will be moreapparent from the following more particular description thereof,presented in conjunction with the following drawings wherein:

FIG. 1A is an axial cross-section view of one embodiment of a lead ofthe present invention;

FIG. 1B depicts a variation on the lead of FIG. 1A;

FIG. 2A is an axial cross-section view of another embodiment of a leadof the present invention;

FIG. 2B depicts a variation on the lead of FIG. 2A;

FIG. 2C is a close-up axial cross-section view of the distal tip of arecording microelectrode and another lead embodiment of the presentinvention;

FIG. 2D is an end view of the lead and microelectrode of FIG. 2C;

FIG. 2E is a cross-section view of the lead of FIG. 2C;

FIG. 2F shows the microelectrode advanced beyond the distal tip of thelead;

FIG. 3 is a cross-section view of another embodiment of a lead of thepresent invention;

FIG. 4A depicts an embodiment of a lead of the present invention with astylet inserted into the lead;

FIGS. 4B-4H depict various configuration of leads of the presentinvention, with stylet removed;

FIG. 5 is one embodiment of a cannula system of the present invention;

FIGS. 6A-6E depict a method of removing a cannula of a cannula system ofthe present invention; and

FIGS. 7A-7B show yet another embodiment of a cannula system of thepresent invention.

Corresponding reference characters indicate corresponding componentsthroughout the several views of the drawings.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best mode presently contemplated forcarrying out the invention. This description is not to be taken in alimiting sense, but is made merely for the purpose of describing thegeneral principles of the invention. The scope of the invention shouldbe determined with reference to the claims.

Traditional procedures for implanting a permanent brain stimulating ordeep brain stimulating (DBS) lead involve several steps, which generallyinclude the following.

-   -   1. Place the stereotactic frame on the subject.    -   2. Perform MRI or equivalent imaging of subject with        stereotactic frame.    -   3. Identify a theoretical target using planning software.    -   4. Place subject with stereotactic frame in head rest.    -   5. Cut skin flap, exposing working surface area of cranium using        scalp clips.    -   6. Place stereotactic arc with target coordinate settings and        identify location on skull for creation of burr hole.    -   7. Remove arc and drill a burr hole in the patient's skull.    -   8. Place the base of the lead anchor.    -   9. With the microelectrode recording drive attached, and with        the appropriate stereotactic frame adaptor inserted into the        instrument guide, place the stereotactic arc.    -   10. Advance a microelectrode cannula and insertion rod into the        brain until they are approximately 25 mm above the target.    -   11. Remove the insertion rod, leaving the cannula in place.    -   12. Insert the recording microelectrode such that the tip of the        microelectrode is flush with the tip of the microelectrode        cannula.    -   13. Attach a connector pin of the recording microelectrode to        the microelectrode recording system.    -   14. Starting approximately 25 mm above the target, begin the        microelectrode recording tract using the microdrive to advance        the microelectrode at a specified rate.    -   15. If the target is identified, proceed to step 16. If the        target is not identified, proceed with the following:        -   a. Using the recording results and the pre-operative            imaging, determine a new set of coordinates for the            theoretical target.        -   b. Disconnect the recording microelectrode from the            microelectrode recording system.        -   c. Remove the recording microelectrode cannula and recording            microelectrode.        -   d. Adjust the coordinates of the stereotactic frame.        -   e. Continue at step 10, above.    -   16. Remove the recording microelectrode cannula and recording        microelectrode.    -   17. Insert a macroelectrode insertion cannula and rod until they        are approximately 25 mm above the target.    -   18. Remove the insertion rod, leaving the macroelectrode        insertion cannula in place.    -   19. Insert a stimulating macroelectrode, and advance to the        target stimulation site identified by the recording        microelectrode.    -   20. Using macrostimulation, simulate the stimulation of the        chronic DBS lead to ensure proper response.    -   21. Remove the macroelectrode and cannula.    -   22. Insert a DBS lead insertion cannula and an insertion rod,        and advance to approximately 25 mm above the stimulation site.    -   23. Remove the insertion rod.    -   24. Insert the DBS lead, with stylet, through the insertion        cannula, and advance to the stimulation site.    -   25. Connect the connector of the lead to a trial stimulator.    -   26. Perform the desired stimulation and measurements using any        one or combination of four electrodes on the DBS lead.    -   27. If the results are favorable, proceed to step 29. If the        results are not favorable, proceed with the following:        -   a. Using the macrostimulation results, microelectrode            recording results, and pre-operative imagining, determine a            new set of coordinates for the theoretical target.        -   b. Remove the lead and stylet.        -   c. Remove the insertion cannula.        -   d. Adjust the coordinates of the stereotactic frame.        -   e. Continue at step 10, above.    -   28. Remove the stylet, followed by the insertion cannula.    -   29. Using macrostimulation, verify that micro-dislodgement of        the DBS lead has not occurred.    -   30. Lock the DBS lead in the lead anchor.

Some physicians might use additional steps, fewer steps, and/or performthe steps in a different order. Obviously, many of these steps cannot beavoided. However, it would be useful if several of these steps could becombined to minimize the total procedure time.

Another problem associated with the standard DBS lead implant proceduresummarized above is micro-dislodgment of the DBS lead when the leadintroduction tools are removed. Implant location is critical withtraditional DBS leads, as a few microns in lead movement can make thedifference between functional and non-functional stimulus therapy. Forthis reason, a straight DBS lead is sometimes implanted withapproximately two electrodes positioned beyond the target location.These electrodes may be able to provide useful stimulation if the leadis pulled in a proximal direction during removal of the introductiontools. Otherwise, repositioning of the lead may be necessary, with theattendant increased risks and expenses. Therefore, systems and methodsto eliminate or minimize micro-dislodgement of the DBS lead would alsobe useful.

In addition, the size and number of holes made in the skull and brainshould be minimized. Minimizing either or both the size of holes and/orthe repositioning rate lowers the chances of perforating a blood vesseland of damaging brain tissue, and lowers the risks of brain damage byreducing brain tissue displacement.

U.S. Pat. No. 6,011,996 discloses a lead assembly including a probe,wherein “[t]he length of probe 33, i.e., from the distal-less surface of[macro-] electrode 32 to the micro-electrode 34, is suitably in therange of 1 to 10 mm, and preferably about 2-5 mm. The length of thisprobe is important, as it establishes the distance between the twoelectrodes . . . . The lead is advanced until the micro-electrode 34discovers the boundary F of the functional structure . . . . ” Since theprobe holds the microelectrode extended a fixed distance from themacroelectrode until the microelectrode is withdrawn, the entireassembly (lead with macroelectrode, microelectrode, and probe) must beadvanced in order to advance the microelectrode.

U.S. Pat. No. 6,066,165 teaches a lead with “electrode contacts coupledto the lead body at the distal end of the lead. [wherein] the lead body. . . defines a sigma shape.” Further, “[t]he sigma segment 20 may asdesired be located at any position along the lead body 12 . . . .[However,] each sigma section 20 is formed only of the lead body 12 . .. . ” Thus, the lead is made of two sections: the lead body and theelectrode(s), and a sigma shape may be positioned only on the lead bodyportion of the lead. Similarly, in U.S. Pat. No. 5,925,073 “a portion ofthe lead body located just proximal of the distal electrode 20 ispreformed to exhibit a wave-like appearance . . . . ”

U.S. Pat. No. 5,843,148 discloses a non-isodiametric chronic DBS leadcomprising a “[l]ead body . . . with a diameter typically of about 0.13cm . . . [and a] distal portion, which carried the ring segmentelectrodes . . . . The outer diameter D4 of the distal portion . . . ispreferably 0.5 mm, but can be in the range of 0.3 to 1.2 mm . . . . ” Inaddition, “[c]ontained within the lead body is a multi-conductor coil32, each conductor being individually insulated, connecting the pulsegenerator to respective electrodes carried by the distal end portion ofthe lead. The lead has a lumen, within coil 32, in which is placed astylet . . . . ” The coil and lumen do not extend into the distalportion of the lead.

U.S. Pat. No. 6,301,492, “provides a microelectrode recording (MER) leadmounted within the central axial channel of a deep brain stimulationlead.” The patent states that since “the [deep brain stimulation lead]is implanted through a cannula which is inserted into the brain . . .[the] stylet . . . is somewhat superfluous as the cannula is rigid andprovides ample stiffness for effective positioning. The presentinvention takes advantage of this by mounting the microelectroderecording (MER) lead in the stylet channel, relying on the cannula toprovide the requisite rigidity.” Similarly, European Patent ApplicationEP 1 062 973 A1 provides “a multifunction electrode device . . .comprising an elongated flexible electrode body having a head sectionthat is provided with a plurality of electrode conductors withassociated electrical connections imbedded in the elongated body,wherein a stilette is provided in the elongated body, said stilettecomprising an insulating coating around an electrically conductoring[sic] core and an exposed microtip where said tip of the stilette can beadvanced through the tip of the electrode body for the performance ofmicroelectrode recordings . . . . The elongated electrode body isprovided in an inflexible insertion tube for the insertion of theelectrode device to the determined implant position.”

A number of cannulas for lead introduction have been proposed, includingcannulas that are splittable. Such cannulas include those that areweakened along their length (e.g., via holes or perforations) and/orinclude a cutting agent (e.g., string or metal strip) allowing them tobe torn, ripped, or cut apart for removal. Cannulas and/or cannulasystems that can be removed with minimal micro-dislodgment of the lead,and that are simple and inexpensive to manufacture are desired.

FIG. 1A is an axial cross-section view of one embodiment of a lead ofthe present invention, which lead can be placed using a stylet 100.Stylet 100 may be solid, hollow (i.e., a tube) or other shape (i.e.,hexagon, square, oval, etc.), and may be made of stainless steel orsimilar material. FIG. 1B is an axial cross-section view of anotherembodiment of a lead that can be placed using stylet 100. The lead mayhave four independent conductors 104, 105, 106, and 107, as shown inFIGS. 1A and 1B, or depending on the application, may have more or fewerconductors. The conductors of the present invention may have a coatingof insulating material, such as ethylene-tetrafluoroethylene (ETFE),polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), orsimilar.

In the embodiment of the invention shown in FIG. 1A, conductors 104,105, 106, and 107 are electrically connected to electrodes 110, 111,112, and 113, respectively, at the distal end of the lead. In theembodiment of the invention shown in FIG. 1B, conductors 104, 105, 106,and 107 are electrically connected to electrodes 126, 111, 112, and 113,respectively, at the distal end of the lead. As seen in FIG. 1B,electrode 126 is a tip electrode.

As with the conductors, the leads have at least one electrode, and morelikely (but not necessarily), have four or more independent electrodes.The electrodes have a surface area in the range of about 1-20 mm², andare made of an electrode material such as platinum, platinum/iridium, orthe like. The electrodes can be cylindrical, semi-cylindrical, circular,semi-circular, or any shape allowing the desired stimulation. Theelectrodes can be, but are not necessarily, equally spaced so that theelectrode array measures around 5-15 mm in length.

The connections between conductors and electrodes are made via crimping,welding, a combination of these, or other suitable means. At theproximal end of the lead, the conductors 104, 105, 106, and 107 areelectrically connected to contacts 116, 117, 118, and 119, via crimping,welding, a combination of these, or other suitable means. These contactsare used to electrically connect the lead to a device that generatesstimulation pulses, which pulses are delivered via the electrodes.Alternatively, the contacts make an electrical connection tointermediate wiring such as a temporary cable.

The lead shown in FIG. 1A has a soft, rounded distal tip 124 made of abiocompatible, insulating polymer, such as silicone, polyurethane, orepoxy. A soft, rounded distal tip made of a polymer may reduce the riskof tissue damage during lead introduction. This same polymer may be usedfor the body 128 of the lead. In contrast, the lead shown in FIG. 1B hasa semi-circular electrode 126 on the distal tip. Electrodes such assemi-circular tip electrodes have different current and densitydistributions than cylindrical electrodes, and so are preferred by somephysicians. Also, a lead with a tip electrode may not need to beadvanced as far into the tissue as a lead with “non-functional” materialat the tip. The outer diameter of the leads of FIGS. 1A and 1B ispreferably, but not necessarily, less than about 1.5 mm (0.060 inch),for instance, less than about 1.25 mm (0.050 inch), or even less thanabout 1 mm (0.040 inch).

FIGS. 2A, 2B, and 2C show additional lead embodiments. These leads havea lumen and through-hole 132 that allow for lead placement over arecording microelectrode wire 134, which may be comprised of one or moreelectrodes. In addition, the lead may be introduced through the samecannula that accommodates the recording microelectrode. The outerdiameter of the leads of FIGS. 2A, 2B, and 2C is preferably similar tothat previously stated for leads of FIGS. 1A and 1B.

In some arrangements, microelectrode wire 134, or a portion ofmicroelectrode wire 134, is coated with insulating compound, such asglass, parylene, or epoxylite, leaving only a very small electrodesurface area 139 (e.g., about 0.01 to 1000 μm²) exposed. Thisconfiguration increases impedance, which is helpful for single cellrecording. As shown in FIGS. 2C-2F, microelectrode wire 134 (not shownin FIGS. 2D and 2E) and surface area 139 are preferably, but notnecessarily, part of a recording microelectrode 135.

Around the microelectrode wire, for instance, a coated microelectrodewire, is an electrode tube 136 of stainless steel or similarly strongmaterial. Electrode tube 136 is preferably, but not necessarily,situated within electrode insulation 138 made of, e.g., polyimide or thelike. Recording microelectrode 135 preferably, but not necessarily, hasa total diameter of about 0.28-0.56 mm (0.011-0.022 inch), such as about0.43-0.46 mm (0.017-0.018 inch) or less.

Conductor winding 140 (wound in helical fashion) forms a lumen 141,allowing a protective tube 130 and microelectrode 135 passage throughthe length of the lead. Insulation 142 surrounds conductor winding 140,and extends from the proximal end of the lead to nearly the distal tipof the lead. Conventional biocompatible insulating material, such assilicone or polyurethane or the like, may be used as insulation 142.

At the distal end of the lead is a tip 144, which may be an electrode,insulating material, or both. Tip 144 may have a countersunk feature 146(shown in FIG. 2C), which stops and centers protective tube 130, ifused, making protective tube 130 (which may also act as a stylet)self-aligning. If tip 144 contains insulating material, the material maybe the same as for insulation 142, or is a material with a higherdurometer, such as 75D polyurethane or epoxy equivalent or the like, toprovide resistance to protective tube 130 pushing against it.

FIG. 2F shows microelectrode 135 advanced beyond the distal tip 144 ofthe lead 128. The ability to independently slide microelectrode 135 andprotective tube 130 allows the lead 128 and microelectrode 135 to beadvanced and retracted in relation to one another. Alternatively,protective tube 130 may be held in place, or may be eliminated.

FIG. 3 shows yet another embodiment of a lead, in cross-section view.The lead of FIG. 3 does not have a lumen for passage of a stylet orrecording microelectrode. Instead, the lead has smaller lumens 150, foraccommodating independent cable conductors 154, which are used ratherthan conventional single-strand wire conductors. As with otherembodiments, the body 128 of the lead may be made of commonly usedbiocompatible insulating material, such as silicone or polyurethane orthe like, and may also be isodiametric. The lead of FIG. 3 may be placedwith a cannula, as one unit.

A configuration as described above allows a lead to have a smallerdiameter since a lumen for the stylet is not required. Therefore, asmaller cannula may be used to place the lead, and thus a smaller holemade through the tissue. The risk of perforating a blood vessel, ordamaging other tissue, is less with a smaller hole. Also, a smaller leaddisplaces less tissue, and this further reduces the risk of tissuedamage, such as brain damage. The outer diameter of the isodiametriclead of FIG. 3 may be less than about 1.25 mm (0.050 inch), forinstance, less than about 1 mm (0.040 inch), or even less than about0.50 mm (0.020 inch).

The lead and lead introduction system embodiments of the presentinvention may be made via standard techniques known by those of ordinaryskill in the art, and may lead to one or more of the following, amongother things:

-   -   1. a reduced number of procedural steps, since one cannula is        used for placing both the recording microelectrode and the lead;    -   2. no need to place a stimulating macroelectrode, since the lead        performs the function of the macroelectrode;    -   3. chronic implantation of the electrode(s) used during        stimulation testing; and    -   4. elimination of the risk of failing to get the electrodes of        the lead to the same location as the microelectrode (usually        caused by insertion of a different cannula for lead placement).

The traditional procedures described earlier for implanting a permanentbrain stimulating or DBS lead, may thus be modified to involve fewersteps, which generally include the following.

-   -   1. Place the stereotactic frame on the subject.    -   2. Perform MRI or equivalent imaging of subject with        stereotactic frame.    -   3. Identify a theoretical target using planning software.    -   4. Place subject with stereotactic frame in head rest.    -   5. Cut skin flap, exposing working surface area of cranium using        scalp clips.    -   6. Place stereotactic arc with target coordinate settings and        identify location on skull for creation of burr hole.    -   7. Remove arc and drill a burr hole in the patient's skull.    -   8. Place the base of the lead anchor.    -   9. With the microelectrode recording drive attached, and with        the appropriate stereotactic frame adaptor inserted into the        instrument guide, place the stereotactic arc.    -   10. Insert an insertion cannula and rod into the brain until        they are approximately 25 mm above the target.    -   11. Remove the insertion rod, leaving the cannula in place.    -   12. Insert a lead and recording microelectrode, with the tip of        the microelectrode flush with the tip of the lead.    -   13. Attach a connector pin of the recording microelectrode to        the microelectrode recording system.    -   14. Starting approximately 25 mm above the target, begin the        microelectrode recording tract using the microdrive to advance        the microelectrode at a specified rate.    -   15. If the target is identified, proceed to step 16. If the        target is not identified, proceed with the following:        -   a. Using the recording results and the pre-operative            imaging, determine a new set of coordinates for the            theoretical target.        -   b. Disconnect the recording microelectrode from the            microelectrode recording system.        -   c. Remove the recording microelectrode, lead and cannula.        -   d. Adjust the coordinates of the stereotactic frame.        -   e. Continue at step 10, above.    -   16. Advance the lead such that the tip of the microelectrode and        the tip of the lead are flush.    -   17. Connect the proximal end of the lead to the distal end of        the External Trial Stimulator (ETS) test cable and connect the        proximal end of the ETS test cable to the ETS.    -   18. Perform the desired stimulation and measurements using any        one or combination of four electrodes on the lead.    -   19. If the results are favorable, proceed to step 29. If the        results are not favorable, proceed with the following:        -   a. Using the recording results and the pre-operative            imaging, determine a new set of coordinates for the            theoretical target.        -   b. Disconnect the recording microelectrode from the            microelectrode recording system.        -   c. Remove the recording microelectrode, lead and cannula.        -   d. Adjust the coordinates of the stereotactic frame.        -   e. Continue at step 10, above.    -   20. Remove the cannula and microelectrode in the order that will        be apparent to the physician.    -   21. Lock the DBS lead in the lead anchor.

Some physicians might use additional steps, fewer steps, and/or performthe steps in a different order. Obviously, many of these steps cannot beavoided. However, it is also obvious that many of the steps previouslyrequired are no longer necessary, using the teachings of the presentinvention.

A lead may also be formed with a shape that enhances lead stability.When a stylet 100 is fully inserted into a lead as shown in FIG. 4A, thelead is essentially straight. As stylet 100 is removed from the lead, apre-formed lead shape, as in one of FIGS. 4B-4H, may appear. Similarly,when recording microelectrode 135 and protective tube 130 are removedfrom the lead, or a cannula is removed from over the lead, thepre-formed shape of the lead appears. Alternatively, due to insertioninto certain tissue, the lead may remain essentially straight, in whichcase the preformed shape will likely provide stabilizing force.

Lead shapes as in FIGS. 4B-4H result from forming the insulation of leadbody 128. In the case of a thermoset insulation material, such assilicone rubber, the tubing may be molded into the pre-formed shapewhile the thermoset is in a green (uncured) state. In the case of athermoplastic insulation material, such as polyurethane, the tubing maybe molded into the pre-formed shape before, during, or after leadassembly, depending on the materials of the lead components, and thetemperature required to shape the insulation being used.

As stated above, FIGS. 4B-4H show various pre-formed shapes that canenhance lead stability. A pre-formed stability feature 160 may bedistal, proximal, or both distal and proximal to electrode array 165,and is preferably, but not necessarily, made of the same material asbody 128. A stability feature distal to the electrode array may reducethe risk of the electrode array moving during cannula withdraw more thanif the feature was proximal to the electrode array. When a curvedstability feature is provided both distal and proximal to the electrodearray, the electrode array is stabilized on both sides, helping tominimize movement. In addition, the distal curve may help stabilize thelead as the cannula is removed over the proximal curve.

FIGS. 4B-4H show pre-formed shapes consisting of a single directioncurve or a bi-directional curve. A potential advantage of abi-directional curve is that the lead is better aligned with thevertical axis. To control the force exerted by the curve(s), theamplitude, spacing, material, and cross-sectional dimensions of thepre-formed curve can be adjusted. In addition, all or some electrodes ofelectrode array 165 may be positioned on a stability feature 160.Theoretical and experimental analysis and testing may be required todetermine what, if any, curve/electrode configuration is ideal foroptimum non-traumatic stabilization of the lead.

As mentioned earlier, another potential item in the lead implantprocedure is the cannula that may be used to guide and support the leadduring implantation. FIG. 5 shows a lead introduction system with aninner cannula 170 and an outer cannula 172. Inner cannula 170 is used toguide the lead into the body tissue. Stabilization of the proximal endof lead 128 is provided with an optional clamp or holder 174, which mayalso include lead attachments used for stimulation and/or recording.Outer cannula 172 is suitably affixed to stereotactic frame 179, and isused to stabilize lead 128 and inner cannula 170 between the skull 176and stereotactic arc 180. This, in turn, may provide better stabilityand control of inner cannula 170 as it travels through the dura mater177 and brain 178. Outer cannula 172 can be used to support variousinner cannulas, e.g., a cannula for placing a recording microelectrodeor stimulating macroelectrode and/or a cannula for placing a lead. Thissystem minimizes the risk of losing the target stimulation site whenchanging cannulas.

FIGS. 6A-6E demonstrate one embodiment of inner cannula 170, and amethod for removing it. In this embodiment, inner cannula 170 issplittable, and may, as shown, have handles 182 at the proximal end. Ashandles 182 are pulled up and away from each other, inner cannula 170splits along a perforated, or similarly splittable interface, from theproximal end toward the distal end, as shown in FIGS. 6A-6E. Outercannula 172 stabilizes the lead during removal of the splittable innercannula 170.

In a related configuration, the sections of inner cannula 170 are heldtogether with a biocompatible glue or the like that breaks when a forceis applied to the cannula. In another embodiment, the sections of innercannula 170 are held together with a clamp or other locking mechanism atthe proximal end. In yet another configuration, inner cannula 170 hastwo sections with a mating wall configuration, similar to a jigsawpuzzle, allowing one half to be slidably removed at a time, whichreduces the chance of dislodging the lead during inner cannula removal.

In another embodiment, inner cannula 170 has slidable sections. In oneconfiguration, the slidable sections are held together by the force ofouter cannula 172, which force can be reduced to allow removal of innercannula 170. For instance, outer cannula 172 may have a slit along itslength, which may be widened and narrowed by, e.g., turning athumbscrew. This allows inner cannula 170 to be removed in sections fromwithin outer cannula 172.

FIGS. 7A and 7B show another embodiment of an inner cannula. Cannula 186has incorporated stimulating macroelectrode(s) 188. FIG. 7A showscannula 186 and recording microelectrode wire 134 in the brain. FIG. 7Bshows cannula 186 and lead 128 in the brain. This embodiment of cannula186 may include one or more of the following aspects, among otherthings:

-   -   1. when the appropriate stimulation site is located with the        recording microelectrode, the stimulating macroelectrodes 188        are in place and ready to deliver test stimulation pulses;    -   2. stimulating macroelectrodes 188 may be advanced over the        recording microelectrode to the exact same anatomical location        as the microelectrode;    -   3. lead 128 may be advanced inside cannula 186 to the exact same        location as stimulating macroelectrodes 188;    -   4. only one cannula insertion is required;    -   5. only one “change-out” of devices inside the cannula is        required;    -   6. bipolar recording/stimulation is possible.

Cannula 186 may be splittable, peelable, slidable, or the like, or maybe configured as described in any of the above embodiments, but this isnot required.

While the invention herein disclosed has been described by means ofspecific embodiments and applications thereof, numerous modificationsand variations could be made thereto by those skilled in the art withoutdeparting from the scope of the invention set forth in the claims. Forinstance, a variety of shapes may be used as a lead stabilizing feature,such as angled features. In another variation, the stabilizing featuresmay project from a straight lead, rather than the lead itself formingthe stabilizing feature. In addition, various lead designs and leadintroduction tools of the present invention may be used for deep brainstimulation, or may be used for stimulating other areas of the body orfor introducing chronic or temporary leads, catheters, or similarlyshaped devices to other locations throughout the body. As such, the word“lead” comprises various types of leads, catheters, and similarly shapeddevices.

1. A method of implanting a brain stimulating lead, consistingessentially of: identifying a theoretical target for brain stimulation;creating a point of entry into the brain; inserting a lead and amicroelectrode into the brain to a position above the theoreticaltarget; advancing the microelectrode toward the theoretical target tolocate a stimulation target; advancing the lead to the stimulationtarget located by the microelectrode; performing test stimulation withthe lead to confirm location of the stimulation target; removing themicroelectrode; and securing the lead, wherein inserting the lead andthe microelectrode comprises, holding a first cannula in a substantiallyfixed position external to the body; slidably supporting a secondcannula with the first cannula; positioning the second cannula with aproximal end extending beyond the proximal end of the first cannula anda distal end extending beyond the distal end of the first cannula andinto the body; inserting the lead and the microelectrode through thesecond cannula; and pulling the second cannula away from the patient'sbrain.
 2. The method of claim 1 wherein at least one of identifying thetheoretical target, creating the point of entry, inserting the lead andthe microelectrode, advancing the microelectrode, and advancing the leadcomprises using a stereotactic frame.
 3. The method of claim 1, whereinthe second cannula includes at least two splittable sections having aperforated interface.
 4. The method of claim 3, wherein pulling thesecond cannula away from the patient's brain further includes, removingat least one splittable section at a time.
 5. The method of claim 3,wherein the second cannula includes at least one handle at the proximalend.
 6. The method of claim 5, wherein the at least one handle isadapted to be pulled up and away from the patient's brain separating thesecond cannula along the perforated interface.
 7. The method of claim 3,wherein the second cannula includes a macroelectrode attached to thedistal end of the second cannula.